From: Hugo Villeneuve Date: Sun, 19 Apr 2026 05:18:54 +0000 (-0700) Subject: Input: charlieplex_keypad - add GPIO charlieplex keypad X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=2ca45e57ea027fffe3350ae5e21ad9cecb0dce74;p=thirdparty%2Fkernel%2Fstable.git Input: charlieplex_keypad - add GPIO charlieplex keypad Add support for GPIO-based charlieplex keypad, allowing to control N^2-N keys using N GPIO lines. Reuse matrix keypad keymap to simplify, even if there is no concept of rows and columns in this type of keyboard. Signed-off-by: Hugo Villeneuve Reviewed-by: Andy Shevchenko Link: https://patch.msgid.link/20260312180304.3865850-5-hugo@hugovil.com Signed-off-by: Dmitry Torokhov --- diff --git a/MAINTAINERS b/MAINTAINERS index 7d10988cbc62..7cf5b55c5973 100644 --- a/MAINTAINERS +++ b/MAINTAINERS @@ -5962,6 +5962,13 @@ S: Maintained F: Documentation/hwmon/powerz.rst F: drivers/hwmon/powerz.c +CHARLIEPLEX KEYPAD DRIVER +M: Hugo Villeneuve +S: Supported +W: http://www.mosaic-industries.com/embedded-systems/microcontroller-projects/electronic-circuits/matrix-keypad-scan-decode +F: Documentation/devicetree/bindings/input/gpio-charlieplex-keypad.yaml +F: drivers/input/keyboard/charlieplex_keypad.c + CHECKPATCH M: Andy Whitcroft M: Joe Perches diff --git a/drivers/input/keyboard/Kconfig b/drivers/input/keyboard/Kconfig index 2ff4fef322c2..9d1019ba0245 100644 --- a/drivers/input/keyboard/Kconfig +++ b/drivers/input/keyboard/Kconfig @@ -289,6 +289,20 @@ config KEYBOARD_MATRIX To compile this driver as a module, choose M here: the module will be called matrix_keypad. +config KEYBOARD_CHARLIEPLEX + tristate "GPIO driven charlieplex keypad support" + depends on GPIOLIB || COMPILE_TEST + select INPUT_MATRIXKMAP + help + Enable support for GPIO driven charlieplex keypad. A charlieplex + keypad allows to use fewer GPIO lines to interface to key switches. + For example, an N lines charlieplex keypad can be used to interface + to N^2-N different key switches. However, this type of keypad + cannot detect more than one key press at a time. + + To compile this driver as a module, choose M here: the + module will be called charlieplex_keypad. + config KEYBOARD_HIL_OLD tristate "HP HIL keyboard support (simple driver)" depends on GSC || HP300 diff --git a/drivers/input/keyboard/Makefile b/drivers/input/keyboard/Makefile index 2d906e14f3e2..60bb7baf802f 100644 --- a/drivers/input/keyboard/Makefile +++ b/drivers/input/keyboard/Makefile @@ -15,6 +15,7 @@ obj-$(CONFIG_KEYBOARD_ATARI) += atakbd.o obj-$(CONFIG_KEYBOARD_ATKBD) += atkbd.o obj-$(CONFIG_KEYBOARD_BCM) += bcm-keypad.o obj-$(CONFIG_KEYBOARD_CAP11XX) += cap11xx.o +obj-$(CONFIG_KEYBOARD_CHARLIEPLEX) += charlieplex_keypad.o obj-$(CONFIG_KEYBOARD_CLPS711X) += clps711x-keypad.o obj-$(CONFIG_KEYBOARD_CROS_EC) += cros_ec_keyb.o obj-$(CONFIG_KEYBOARD_CYPRESS_SF) += cypress-sf.o diff --git a/drivers/input/keyboard/charlieplex_keypad.c b/drivers/input/keyboard/charlieplex_keypad.c new file mode 100644 index 000000000000..6dbb5c183f02 --- /dev/null +++ b/drivers/input/keyboard/charlieplex_keypad.c @@ -0,0 +1,232 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * GPIO driven charlieplex keypad driver + * + * Copyright (c) 2026 Hugo Villeneuve + * + * Based on matrix_keyboard.c + */ + +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include + +struct charlieplex_keypad { + struct input_dev *input_dev; + struct gpio_descs *line_gpios; + unsigned int nlines; + unsigned int settling_time_us; + unsigned int debounce_threshold; + unsigned int debounce_count; + int debounce_code; + int current_code; +}; + +static void charlieplex_keypad_report_key(struct input_dev *input) +{ + struct charlieplex_keypad *keypad = input_get_drvdata(input); + const unsigned short *keycodes = input->keycode; + + if (keypad->current_code > 0) { + input_event(input, EV_MSC, MSC_SCAN, keypad->current_code); + input_report_key(input, keycodes[keypad->current_code], 0); + input_sync(input); + } + + if (keypad->debounce_code) { + input_event(input, EV_MSC, MSC_SCAN, keypad->debounce_code); + input_report_key(input, keycodes[keypad->debounce_code], 1); + input_sync(input); + } + + keypad->current_code = keypad->debounce_code; +} + +static void charlieplex_keypad_check_switch_change(struct input_dev *input, + unsigned int code) +{ + struct charlieplex_keypad *keypad = input_get_drvdata(input); + + if (code != keypad->debounce_code) { + keypad->debounce_count = 0; + keypad->debounce_code = code; + } + + if (keypad->debounce_code != keypad->current_code) { + if (keypad->debounce_count++ >= keypad->debounce_threshold) + charlieplex_keypad_report_key(input); + } +} + +static int charlieplex_keypad_scan_line(struct charlieplex_keypad *keypad, + unsigned int oline) +{ + struct gpio_descs *line_gpios = keypad->line_gpios; + DECLARE_BITMAP(values, MATRIX_MAX_ROWS); + int err; + + /* Activate only one line as output at a time. */ + gpiod_direction_output(line_gpios->desc[oline], 1); + + if (keypad->settling_time_us) + fsleep(keypad->settling_time_us); + + /* Read input on all other lines. */ + err = gpiod_get_array_value_cansleep(line_gpios->ndescs, line_gpios->desc, + line_gpios->info, values); + + gpiod_direction_input(line_gpios->desc[oline]); + + if (err) + return err; + + for (unsigned int iline = 0; iline < keypad->nlines; iline++) { + if (iline == oline) + continue; /* Do not read active output line. */ + + /* Check if GPIO is asserted. */ + if (test_bit(iline, values)) + return MATRIX_SCAN_CODE(oline, iline, + get_count_order(keypad->nlines)); + } + + return 0; +} + +static void charlieplex_keypad_poll(struct input_dev *input) +{ + struct charlieplex_keypad *keypad = input_get_drvdata(input); + int code = 0; + + for (unsigned int oline = 0; oline < keypad->nlines; oline++) { + code = charlieplex_keypad_scan_line(keypad, oline); + if (code != 0) + break; + } + + if (code >= 0) + charlieplex_keypad_check_switch_change(input, code); +} + +static int charlieplex_keypad_init_gpio(struct platform_device *pdev, + struct charlieplex_keypad *keypad) +{ + char **pin_names; + char label[32]; + + snprintf(label, sizeof(label), "%s-pin", pdev->name); + + keypad->line_gpios = devm_gpiod_get_array(&pdev->dev, "line", GPIOD_IN); + if (IS_ERR(keypad->line_gpios)) + return PTR_ERR(keypad->line_gpios); + + keypad->nlines = keypad->line_gpios->ndescs; + + if (keypad->nlines > MATRIX_MAX_ROWS) + return -EINVAL; + + pin_names = devm_kasprintf_strarray(&pdev->dev, label, keypad->nlines); + if (IS_ERR(pin_names)) + return PTR_ERR(pin_names); + + for (unsigned int i = 0; i < keypad->line_gpios->ndescs; i++) + gpiod_set_consumer_name(keypad->line_gpios->desc[i], pin_names[i]); + + return 0; +} + +static int charlieplex_keypad_probe(struct platform_device *pdev) +{ + struct charlieplex_keypad *keypad; + struct input_dev *input_dev; + unsigned int debounce_interval_ms = 5; + unsigned int poll_interval_ms; + int err; + + keypad = devm_kzalloc(&pdev->dev, sizeof(*keypad), GFP_KERNEL); + if (!keypad) + return -ENOMEM; + + input_dev = devm_input_allocate_device(&pdev->dev); + if (!input_dev) + return -ENOMEM; + + keypad->input_dev = input_dev; + + err = device_property_read_u32(&pdev->dev, "poll-interval", &poll_interval_ms); + if (err) + return dev_err_probe(&pdev->dev, err, + "failed to parse 'poll-interval' property\n"); + + if (poll_interval_ms == 0) + return dev_err_probe(&pdev->dev, -EINVAL, "invalid 'poll-interval' value\n"); + + device_property_read_u32(&pdev->dev, "debounce-delay-ms", &debounce_interval_ms); + device_property_read_u32(&pdev->dev, "settling-time-us", &keypad->settling_time_us); + + keypad->current_code = -1; + keypad->debounce_code = -1; + keypad->debounce_threshold = DIV_ROUND_UP(debounce_interval_ms, poll_interval_ms); + + err = charlieplex_keypad_init_gpio(pdev, keypad); + if (err) + return err; + + input_dev->name = pdev->name; + input_dev->id.bustype = BUS_HOST; + + err = matrix_keypad_build_keymap(NULL, NULL, keypad->nlines, + keypad->nlines, NULL, input_dev); + if (err) + return dev_err_probe(&pdev->dev, err, "failed to build keymap\n"); + + if (device_property_read_bool(&pdev->dev, "autorepeat")) + __set_bit(EV_REP, input_dev->evbit); + + input_set_capability(input_dev, EV_MSC, MSC_SCAN); + + err = input_setup_polling(input_dev, charlieplex_keypad_poll); + if (err) + return dev_err_probe(&pdev->dev, err, "unable to set up polling\n"); + + input_set_poll_interval(input_dev, poll_interval_ms); + + input_set_drvdata(input_dev, keypad); + + err = input_register_device(keypad->input_dev); + if (err) + return err; + + return 0; +} + +static const struct of_device_id charlieplex_keypad_dt_match[] = { + { .compatible = "gpio-charlieplex-keypad" }, + { } +}; +MODULE_DEVICE_TABLE(of, charlieplex_keypad_dt_match); + +static struct platform_driver charlieplex_keypad_driver = { + .probe = charlieplex_keypad_probe, + .driver = { + .name = "charlieplex-keypad", + .of_match_table = charlieplex_keypad_dt_match, + }, +}; +module_platform_driver(charlieplex_keypad_driver); + +MODULE_AUTHOR("Hugo Villeneuve "); +MODULE_DESCRIPTION("GPIO driven charlieplex keypad driver"); +MODULE_LICENSE("GPL");